The present invention relates to a process for piecing a thread in an open-end spinning apparatus having a fibre collection surface, in which process a sliver is supplied to the clothing of an opening cylinder and is opened thereby into fibres and is supplied in this form to the fibre collection surface, where the fibres are incorporated into the end of a returned thread which is then drawn off continuously, and to an apparatus for carrying out this process.
When piecing, the problem arises that on the one hand the returned thread end and the supplied fibres form an overlapping point which forms a thick point in the joint. On the other hand, the thread must be accelerated to production draw-off speed. If this acceleration takes place too slowly, then a thick point is again produced in the joint. However, if this acceleration takes place too quickly, then there is a risk of thread breakage because of the high draw-off tension. To solve these problems, it is known from WO 88/10990 to determine the combing state of the tuft and to match the thread draw-off to the effectiveness of fibre supply to the fibre collection surface. It is furthermore known from this specification to begin the drawing off of the thread at a low acceleration even before the fibres reach the fibre collection surface and only after the fibres then supplied to the fibre collection surface have contacted the thread end to increase the rate of drawing off of the thread. In this way, although a substantial reduction in the thick point in the joint is achievable, the joint is still disruptive for certain purposes.